The family Enterobacteriaceae are known to include many genera of bacteria which produce biochemically useful products such as the L-histine-producing bacterium, Serratia marcescens ATCC 31026; L-threonine-producing bacteria, Providencia rettgeri ATCC 21118, Proteus vulgaris ATCC 21117, Klebsiella pneumoniae ATCC 21316 and Escherichia coli ATCC 21278; L-valine-producing bacterium, Citrobacter freundii ATCC 11102; 2-ketogluconic acid-producing bacterium, Erwinia herbicola ATCC 21998; polynucleotide phosphorylase-producing bacterium, Proteus mirabilis ATCC 21635; and Enterobacter cloacae ATCC 15337 having insecticidal property against Lepidoptera. The fermentative production of each product involves complex biochemical pathways controlled by multiple genes and gene products. The fermentative products are produced in relatively low amounts. It would be advantageous if the fermentative production of these useful biochemicals could be enhanced.